1. Field Of The Invention
The invention relates to a process for the production of gamma-butyrobetaine.
2. Background Art
Gamma-butyrobetaine is finding increasing use as an initial product for the microbiological production of L-carnitine. Laboratory processes for the synthesis of the individual intermediate steps have been sufficiently described.
According to West German OS 2,751,134, gamma-butyrolactone can be reacted with thionyl chloride and methanol in a 91 percent yield into 1-chlorobutyric acid methyl ester. The necessary disposal of the resultant SO.sub.2 is a drawback in this process.
It can be seen from West German OS 1,903,076 that gamma-butyrolactone can be converted into the gamma-chlorobutyric acid methyl ester with dry hydrochloric acid and methanol with 4-hour refluxing and after one-week standing of the reaction solution.
It can be gathered from West Germany OS 1,939,759 that gamma-butyrolactone can be converted into the gamma-chlorobutyric acid methyl ester in a two-step process (first step with zinc chloride and hydrochloric acid; second step with methanol under reflux conditions) with a yield of 90 to 95 percent. But a great disadvantage is the amount of zinc salt formed that cannot be recycled and heavily loads the waste water.
From Aksnes et al., J. Chem. Soc., (1959), p. 103 ff, it is further known that gamma-bromobutyric acid methyl ester can be converted into the 4-trimethylammonium butyric acid methyl ester by heating with alcoholic trimethylamine in a yield of only 20 percent.
The above-mentioned process steps, thus, produce either highly unsatisfactory yields or, because of the disposal problems of the resulting by-products, are not feasible on a commercial scale.